feat: SQL 语法支持 BETWEEN AND、DROP TABLE IF EXISTS

src/sql/parser.ts

@@ -423,8 +423,15 @@ export class Parser {
   private parseDropTable(): DropTableStatement {
     this.expect(TokenType.DROP);
     this.expect(TokenType.TABLE);
+    // IF EXISTS（可选）
+    let ifExists = false;
+    if (this.curTokenIs(TokenType.IF)) {
+      this.nextToken();
+      this.expect(TokenType.EXISTS);
+      ifExists = true;
+    }
     const tableName = this.expectIdentifier('table name');
-    return { type: 'DROP_TABLE', name: tableName };
+    return { type: 'DROP_TABLE', name: tableName, ifExists: ifExists || undefined };
   }
 
   // ===================================================================
@@ -483,6 +490,29 @@ export class Parser {
       return result;
     }
 
+    // BETWEEN val1 AND val2
+    if (this.curTokenIs(TokenType.BETWEEN)) {
+      this.nextToken();
+      const low = this.parseValue();
+      this.expect(TokenType.AND);
+      const high = this.parseValue();
+      const result: WhereCondition = {};
+      result[column] = { $gte: low, $lte: high };
+      return result;
+    }
+
+    // NOT BETWEEN val1 AND val2
+    if (this.curTokenIs(TokenType.NOT) && this.peekTokenIs(TokenType.BETWEEN)) {
+      this.nextToken(); // skip NOT
+      this.nextToken(); // skip BETWEEN
+      const low = this.parseValue();
+      this.expect(TokenType.AND);
+      const high = this.parseValue();
+      const result: WhereCondition = {};
+      result[column] = { $not: { $gte: low, $lte: high } };
+      return result;
+    }
+
     // NOT LIKE / NOT IN（NOT 后紧跟 LIKE 或 IN）
     if (this.curTokenIs(TokenType.NOT)) {
       if (this.peekTokenIs(TokenType.IN)) {